Fwd: Can a task on each of 2 processors share 7 GB of physical memory
Fwd: Can a task on each of 2 processors share 7 GB of physical memory
- Subject: Fwd: Can a task on each of 2 processors share 7 GB of physical memory
- From: Jonas Maebe <email@hidden>
- Date: Thu, 13 Nov 2003 11:19:36 +0100
Hello,
Given the recent discussion here about 64 bit memory addressing on this
list, I thought this might be interesting. It seems you can access more
than 4GB of memory from one process by playing a bit with mmap and
friends. You just cannot have it all mapped in your process at the same
time.
Jonas
Begin forwarded message:
From: Quinn <email@hidden>
Date: don nov 13, 2003 10:58:46 Europe/Brussels
To: "'email@hidden'" <email@hidden>
Subject: Re: Can a task on each of 2 processors share 7 GB of
physical memory
At 18:37 -0800 12/11/03, Miller, Larry wrote:
[snip]
And I would like to have a
task on each of the two processors have direct access (thru pointer
dereferencing) to this 7 GB worth of memory.
This indicates that you want to access > 4 GB of memory from a single
process via direct pointer access. Do I understand you correctly?
If so, this can't be done on G5 systems running current versions of
Mac OS X. Currently all processes have a 32-bit address space and run
in 32-bit mode. Therefore no process can directly access more than 4
GB of memory (the limit is less if you consider the address space
consumed for frameworks etc).
That's not to say that the G5's large physical memory is useless. It
allows you to run multiple processes, each with a huge working set.
You can also indirectly access large memory spaces by changing the
memory mappings within your process. However, both of these are
outlawed by your problem statement.
Apple is aware of the need for supporting 64-bit address spaces.
However, I'm not authorised to say anything about our plans in this
area.
S+E
--
Quinn "The Eskimo!"
<http://www.apple.com/developer/>
Apple Developer Technical Support * Networking, Communications,
Hardware
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